Trim indicator and circuit therefor

ABSTRACT

A trim or tilt angle-indicating system for providing a visual indication of the position angle of the outdrive unit in an inboard-outboard boat propulsion system including an electrical meter coupled in a bridge circuit supplied power by a regulated voltage supply. One leg of the bridge circuit comprises a variable resistor which has a wiper arm coupled to the outdrive unit. As the trim angle of the outdrive is varied, the resistance of the variable resistor changes, to thereby unbalance the bridge circuit. The resulting electrical current flow through the meter deflects a meter needle to indicate that the trim angle of the outdrive unit on a dial is associated with the meter.

United States Patent [191 Carpenter et al.

[ 1 TRIM INDICATOR AND CIRCUIT THEREFOR [75] Inventors: William R.Carpenter; Richard M. Sponaas, both of Muskegon, Mich.

[73] Assignee: Medallion Instruments, Inc., Spring Lake, Mich.

[22] Filed: Nov. 8, 1971 [21] Appl. N0.: 196,325

[52] US. Cl......' 115/41 HT [51] Int. Cl B63h 5/12 [58] Field of Search115/41 R, 41 HT, 34, 35; 340/177 R,210; 324/57,76, 110, 105; 307/318,297

[56] References Cited UNITED STATES PATENTS 2,871,701 2/1959 Knudsen324/105 3.207.984 9/1965 Tolliver 324/105 3.495.159 2/1970 Smith 324/1053.641.965 Z/1972 Schmiedel 244/41 HT 3.671.952 6/1972 Simms. Jr 340/177R 3.237.186 2/1966 Whelpley et a1. 340/177 R X [451 -Mar. 19, 19743,521,589 7/1970 Kemp 115/35 X 3,054,095 9/1962 Heller 340/210 X2,745,087 5/1956 Dickinson 340/177 R 2,599,258 6/1952 l-ioare 340/210 X[57] ABSTRACT A trim or tilt angle-indicating system for providing avisual indication of the position angle of the outdrive unit in aninboard-outboard boat propulsion system including an electrical metercoupled in a bridge circuit supplied power by a regulated voltagesupply. One leg of the bridge circuit comprises a variable resistorwhich has a wiper arm coupled to the outdrive unit. As the trim angle ofthe outdrive is varied, the resistance of the variable resistor changes,to thereby unbalance the bridge circuit. The resulting electricalcurrent flow through the meter deflects a meter needle to indicate thatthe trim angle of the outdrive unit on a dial is associated with themeter.

4 Claims, 2 Drawing Figures HYDRAULIC 42 SYST EM TO LOWER UNlT ClLlNDERPATENTEDHAR 19 I974 35 HYDRAULIC SYSTEM m l {42w PPJOR ART FIG /HYDRAULIC SYSTEM I I V T0 LOWER UNIT CYUNUER TRIM INDICATOR AND CIRCUITTHEREFOR BACKGROUND OF THE INVENTION The present invention relates to atrim (i.e., tilt) angle indicator and circuit therefor to indicate thetrim angle of an outdrive unit for an inboard-outboard boat.

.In boats employing an inboard-mounted drive motor and anoutboard-mounted lower unit (outdrive), which are commonly known asinboard-outboard boats, the outdrive unit is relatively heavy andinaccessible or un-. wieldy as compared with an outboard motor, most ofwhich can be manually raised by pivoting the motor about the transom ofthe boat. Thus, with the inboardoutboard system, an electricallyoperated hydraulic unit is provided for raising and lowering theoutdrive unit. Frequently, an electrical meter is also provided suchthat the trim angle of the outdrive unit (i.e., the angle of the unitwith relation to the surface of the water) is, in one manner or another,indicated to the operator at the pilot house or dashboard of the boat.

In some of the known instruments for indicating the trim angle of thelower unit, a sensing and drive circuit for the electrical metermovement includes a pair of coils coupled to a sensing resistor. Theresistance of the sensing resistor is varied as a function of the trimangle of the outdrive unit, by mechanically connecting the wiper armofthe variable resistor to the outdrive. The meter for indicating thetrim angle is coupled directly to the electrical supply system of theboat (commonly a storage battery) which is also used to supply currentto the electrical motor for raising and lowering the outdrive unit. Whenthe outdrive unit is raised, theelectrical drive motor, which requires aconsiderable amount of current to raise the heavy outdrive unit, causesthe battery voltage to decrease. Since the battery supplies the trimangle indicator, the meter will under these circumstances indicate anerroneous trim angle, due to the varying supply voltage. Additionally,since the trim angle indicator iscoupled directly to the battery of theboat, other electricaldisturbances such as inductive voltage spikescaused by the operation of accessories or other electricalequipment onthe boat affects the reading provided by the trim indicator and cancause erroneous or spurious readings.

SUMMARY OF THE PRESENT INVENTION The trim-indicating meter system of thepresent invention eliminates, and is free of'the sources of erroneousindication found in prior indicating systems and at the same time ismore sensitive and accurate than the latter. In accordance with thepresent invention, the indicating meter is connected in a bridge circuitand, furthermore, such circuit is supplied operating power from aregulated voltage source. The supply for the meter instrument thereforedoes not fluctuate with changing battery voltage due to current drawn bythe drive motor for the outdrive, or due to the actuation of otherelectrical equipment on the boat. Asensing resistor having a resistancewhich varies in response to the position of the lower unit is coupled inone leg of the bridge circuit to vary the current through the indicatingmeter as the trim angle of the outdrive unit is varied. A pointer needleassociated with the meter provides an accurate trim angle indication onan associated dial.

BRIEF DESCRIPTION OF THE DRAWINGS of a boat with an outdrive unit; and

FIG. 2 is an electrical circuit diagram in schematic form showing thecontrol circuit for an electrically operated hydraulic outdrive andshowing the trim angle indicator and circuit of the present invention.

DETAILED DESCRIPTIONOF PREFERRED EMBODIMENT In FIG. 1 there is shown aninboard-outboard boat 10 having an inboard engine (not shown) and anoutdrive unit 12 coupled to the engine and mounted to the transom 14 ofboat 10. Unit 12 includes a propeller l3 driven by the inboard enginefor propelling the boat through the water. The outdrive 12 is pivotallycoupled to the transom 14 such that it can be raised or lowered by ahydraulic cylinder 16 which is normally mounted on the hull or transom,or within the engine compartment of the boat 10. The hydraulic cylinder16 has a movable shaft or ram 17 coupled to the outdrive unit 12 suchthat as the shaft is extended or retracted the outdrive will be raisedand'lowered. Additionally, the lower unit 12 or at least its propellersection can be turned from side to side to control the direction of boattravel.

When the boat is in motion, it is frequently desired to vary the angularposition (trim angle) of the outdrive unit 12 to achieve maximumperformance of the boat. Also, when the boat is beached or is goingthrough shallow water, the outdrive unit 12 must be in a raised orpartially raised position. The raising and lowering of unit 12 isachieved by actuating the hydraulic cylinder 16 by a control circuitsuch as thatshown at 20 in FIG. 1. Hydraulic pressure is supplied to thecylinder 16 by means of a coupling such as a hose indicated by thedotted line 15 between cylinder 16 and the hydraulic system 40 inFIG. 1. It is to be understood that the control circuit 20, the motor 30and system 40 are mounted within the hullof boat 10. The hydraulicsystem 40 includes a hydraulic pump mechanically driven by theelectrical motor 30.

The electrical control system 20 comprises a first push button switch 22having one terminal coupled to a positive terminal on a battery 25 and aterminal remote from this junction coupled to a first motor winding 32associated with the'motor 30. A second switch 24 similarly has oneterminal coupled to the positive terminal of battery 25 and a terminalremote from this junction coupled to a third push button switch 26.Parallel with the switch 26 as shown is a limit switch 27. The terminalof switch 26 remote from its junction with switch 24 is coupled to oneterminal of a limit switch 28 having a terminal remote from its junctionwith push button switch 26 coupled to one terminal of a relay coil 29.The terminal of relay 29 remote from switch 28 is coupled to a referencepotential such as ground as shown in FIG. 1. The negative terminal ofbattery 25 is likewise coupled to ground.

Relay 29 has a pair of normally open contacts 29 having one terminalcoupled to the positive terminal of battery 25 and the other terminalcoupled to a second motor winding 34 associated with motor 30. windings32 and 34 of motor 30 are coupled to a first terminal 31 on the motor 30which has a second terminal 33 coupled to ground. Motor 30 has anarmature shaft which is mechanically coupled to the hydraulic pump inthe hydraulic system 40, as indicated by the dotted line 35 in FIG. 1.

An indicator 50 of a type presently in use includes a meter having afirst coil 52 coupled from the positive terminal of battery 25 toground, and a second coil 54 coupled to the positive terminal of battery25 by means of a resistor 53. The end of coil 54 remote from thejunction to resistor 53 is returned to ground. The meter includes apermanent magnet 55 disposed in physical proximity to the coils 52 and54 such that a varying magnetic field developed by coils 52 and 54 dueto current therethrough will cause the permanent magnet 55 to rotate. Asensing resistor 60 comprising a rheostat or potentiometer with a wiperarm 62 is coupled in paral lel with coil 54. The wiper arm 62 ismechanically coupled to a movable element within the hydraulic system 40as indicated by the dashed lines in the figure. As the outdrive unit istilted, the movable element causes wiper arm 62 to move to vary theresistance of resistor 62 so asto change the direction of the magneticfield produced by coils 52 and 54 due to the changing current divisionbetween coils 52 and 54. A meter needle 56 is coupled to the magnet 55and moves therewith to provide an indication between the meter needle 56and a dial scale (not shown) calibrated to show the trim angle of theoutdrive l2.

Limit switch 27 is normally closed and opens only when the outdrive unit12 is raised to a predetermined maximum position. Switch 26 can beactuated to override this limit switch if desired; however, the limitswitch 28 is an absolute end-of-travel limit switch which opens onlywhen the outdriveunit 12 is in a fully raised position to prevent damageto the outdrive unit 12 by further actuation of the motor 30. To raisethe outdrive, the push button switch 24is actuated. With the limitswitches 27 and 28 in their normally closed position relay 29 isactuated through the closed switch 24 and switches 27 and 28 such thatthe contacts 29 associated with the relay 29 are closed. The closing ofrelay contacts 29' couples the motor winding 34- to battery 25. Theresulting current through motor winding 34 causes the motor shaft 35 torotate in the direction to extend the'hydraulic ram shaft 17 of thehydraulic cylinder 16, thereby raising the outdrive 12. It is to benoted that relay 29 is required to raise the out-drive unit since theswitches 34, 27, and 28 cannot carry the relatively large current drawnthrough winding 34 of motor 30 to raise the unit 12.

As the outdrive unit 12 is raised, the resistance of resistor 60increases thereby increasing the current in coil 54 of the indicator 50.The wiper arm 62 can be coupled toany convenient location in thehydraulic system or directly to the outdrive unit 12. It has beenconvenient to provide a small hydraulic cylinder 42 having a movableshaft 43 that tracks the raising and lowering of the outdrive unit 12and to which the wiper arm 62 is coupled.

To lower the outdrive 12, switch 22 is actuated, closing the contacts tocouple motor winding 32 to the battery 25. No relay is needed forwinding 32 since considerably less current is drawn when the unit 12 islowered. When lowering the outdrive 12, the resistance of resistor 60decreases and, therefore, the current in coil 54 of the indicator 50decreases to cause the needle 56 mounted on the permanent magnet 55 tochange position in a direction corresponding to the movement of theoutdrive unit 12. It is noted that the internal resistance of coil 52 issufficient to prevent damage of the meter.

Since the indicator 50 is directly coupled to the battery 25, batteryvoltage fluctuations, as for example as a result of the actuation ofmotor winding 34 when the outdrive unit 12 is raised, adversely affectthe operation of the indicator 50, tending to cause erroneous andspurious readings. Similarly, once the outdriveelevating push buttonswitch 24 is released, the induced reverse voltage spike caused by theinterruption of current through coil 34 is applied directly to theindicator 50 since the relay contacts 29 cannot open as quickly as thevoltage spike is developed. This induced voltage spike further adverselyaffects the operation of the prior art indicator 50 of FIG. 1.

Referring now to FIG. 2, there is shown an improved indicating unitwhich can be used with a control circuit substantially the same as thatshown in FIG. 1. Circuit elements of FIG. 2 which are the same as thatshown in FIG. 1 are labeled with identical reference numerals. Thecontrol circuit 20 of FIG. 2 operates in the same manner as circuit 20of FIG. 1 to raise and lower the outdrive 12 (not shown in FIG. 1).

The indicating unit 70 includes a voltage regulator coupled to thebattery 25 comprising a current-limiting resistor 71 having one endcoupled to the positive terminal battery 25 and an end remote therefromcoupled to the cathode of a zener diode 72. The anode of the zener diodeis returned to ground, as is the negative terminal of battery 25.Resistor 71 is chosen to bias the zener diode 72 in an avalanche mode ofoperation such that the voltage across the diode 72 will remain constantwithin the ranges of voltage fluctuations of battery 25. A bridgecircuit comprises four resistors 73, 74, 60 and 80. Resistors 73 and 74are joined at a first input terminal 93 and resistors 60 and 80 arejoined at a second input terminal such as ground. Resistor 60 isvariable, having a wiper arm 62 coupled to a sending unit such asmovable element 43 of a small hydraulic cylinder 42 in the hydraulicsystem 40. The element 43 accurately tracks the position of (i.e.,follows in a predetermined relationship) outdrive unit 12. Thus, as theoutdrive 12 moves the wiper arm 62 is correspondingly moved, causing theresistance of resistor 60 to vary to provide a resistance which is afunction of the outdrive 12 position.

An indicating meter 75 is coupled from a first bridge terminal at thejunction of resistors 74 and 80 to a second bridge terminal 96 at thejunction of resistors 73 and 60.

The meter 75 comprises a dual magnet type of meter, actuated by a singlecoil 76 and including permanent magnets 77 and 78, to which ismechanically coupled a meter needle 79. This type of meter movement isinsensitive to external magnetic fields and responds only to themagnetic field set up by the current flowing through coil 76, to providea needle deflection corresponding to the trim angle of the outdrive unit12.

The resistance values of resistors 73 and 74 are identical andresistance of resistor 80 is chosen such that it will match the nominalresistance of resistor 60 when the outdrive unit 12 is at its midpoint.In this position of unit 12, the bridge 85 is balanced and no currentflows through meter 75. When the resistance of resistor 60 varies as theoutdrive unit 12 is raised or lowered, the bridge will become unbalancedthereby causing current to flow through the indicating meter 75 in a direction from terminal 95 to terminal 96 or from terminal 96 to 95. Sincethe operating power for bridge 85 is a regulated voltage source, themeter 75 will not respond to battery voltage fluctuations caused by theactuation of the raising and lowering windings 34 and 32, respectivelyof the outdrive unit 12 or actuation of other electrical equipment onthe boat. Thus only variations in the position of outdrive 12 willdeflect the needle 79 of meter 75, which therefore accurately indicatesthe position of unit 12.

Electrical circuitparameters which have been employed in a specificpreferred working embodiment include the following: resistor 71 30 ohms;diode 72 6.8 volt zener; resistor 73 220 ohms; resistor 74 220 ohms;resistor 60 0 to 150 ohms, linear wound, the zero end corresponding tothe lowered position of outdrive unit 12; resistor 80 75 ohms; and theresistance of coil 76 within meter 75 ohms; battery 25 12 volts DC. Thecomponents of the indicator 70, with the exception of theremotely-mounted resistor 60, can be mounted within the case 82 of themeter 75 which, as shown in FIG. 2, can be grounded to shield thecomponents.

, In accordance with the foregoing, the present inven tion provides anindicating system for the particular type of application described whicheliminates the operational problems and short-comings of systemspresently available or in use and which provides greatly improvedresults. It is entirely conceivable that upon examining the foregoingdisclosure, those skilled in the art may devise embodiments of theconcept involved which differ somewhat from the embodiment shown anddescribed herein, or may make various changes in structural details tothe present embodiment. Consequently, all such changed embodiments orvariations in structure which utilize the concepts of the invention andclearly incorporate the spirit thereof are to be considered as withinthe scope of the claims appended herebelow, unless these claims by theirlanguage specifically state otherwise.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. For use in marine craft having an outboard-type drive train includingan outdrive unit with an electrically actuated system for raising andlowering the outdrive unit to change its trim angle, a trim angleindicator including a meter movement having a meter needle forindicating the trim angle of the outdrive unit, said indicatorcomprising: a voltage regulator having input terminals for coupling saidregulator to a source of operating potential, and having outputterminals; a bridge network including a variable resistor having amovable wiper arm for varying the resistance of said variable resistor,said bridge having first and second input terminals coupled to saidoutput terminals of said voltage regulator, said bridge also havingfirst and second output terminals; said meter movement coupled to saidfirst and second output terminals of said bridge; and means for movingsaid wiper arm of said variable resistor as the trim position of theoutdrive unit changes, to vary the resistance of said variable resistorthereby causing an electrical current to flow through said metermovement and thereby causing the latter to indicate the trim position ofthe outdrive Unit.

2. The indicator as defined in claim 1 wherein said means for movingsaid wiper arm of said variable resistor comprises: a movable element insaid system for raising and lowering the outdrive unit and a mechanicalcoupling means for connecting said wiper arm to said movable elementsuch that said wiper arm tracks the position of the outdrive unit.

3. The indicator as defined in claim 1 wherein said voltage regulatorcomprises a zener diode coupled between said output terminals of saidvoltage regulator and means biasing said diode in the avalanche mode ofoperation when said voltage regulator is coupled to a source ofoperating potential.

4. The indicator as defined in claim 3 wherein one of said inputterminals of said voltage regulator is coupled to one of said outputterminals of said voltage regulator and wherein said means biasing saiddiode comprises a current limiting resistor coupled between the other ofsaid input terminals and the other of said output terminals, such thatsaid resistor biases said zener diode in an avalanche mode of operationand limits current flowing through said diode.

1. For use in marine craft having an outboard-type drive train includingan outdrive unit with an electrically actuated system for raising andlowering the outdrive unit to change its trim angle, a trim angleindicator including a meter movement having a meter needle forindicating the trim angle of the outdrive unit, said indicatorcomprising: a voltage regulator having input terminals for coupling saidregulator to a source of operating potential, and having outputterminals; a bridge network including a variable resistor having amovable wiper arm for varying the resistance of said variable resistor,said bridge having first and second input terminals coupled to saidoutput terminals of said voltage regulator, said bridge also havingfirst and second output terminals; said meter movement coupled to saidfirst and second output terminals of said bridge; and means for movingsaid wiper arm of said variable resistor as the trim position of theoutdrive unit changes, to vary the resistance of said variable resistorthereby causing an electrical current to flow through said metermovement and thereby causing the latter to indicate the trim position ofthe outdrive unit.
 2. The indicator as defined in claim 1 wherein saidmeans for moving said wiper arm of said variable resistor comprises: amovable element in said system for raising and lowering the outdriveunit and a mechanical coupling means for connecting said wiper arm tosaid movable element such that said wiper arm tracks the position of theoutdrive unit.
 3. The indicator as defined in claim 1 wherein saidvoltage regulator comprises a zener diode coupled between said outputterminals of said voltage regulator and means biasing said diode in theavalanche mode of operation when said voltage regulator is coupled to asource of operating potential.
 4. The indicator as defined in claim 3wherein one of said input terminals of said voltage regulator is coupledto one of said output terminals of said voltage regulator and whereinsaid means biasing said diode comprises a current limiting resistorcoupled between the other of said input terminals and the other of saidoutput terminals, such that said resistor biases said zener diode in anavalanche mode of operation And limits current flowing through saiddiode.